Perpendicular Constraint
- Select Drawing | Constraints |  Add perpendicular constraint. Add perpendicular constraint.
- Select a line (A).
- Select a second line (B).

 Select line elements, and then select the Constraints> Perpendicular function from the context-sensitive menu.
 Select line elements, and then select the Constraints> Perpendicular function from the context-sensitive menu.
Note: 
      
  - When drawing a rectangle using the  Rectangle function, the corners will be perpendicular. Rectangle function, the corners will be perpendicular.
- If you add a line perpendicular to another line by using the T key, a perpendicular constraint is automatically created.
